Fiber-reinforced resin pipes containing a thermoset resin or a thermoplastic resin as the matrix resin conventionally have been produced by several winding techniques including the filament winding method, the tape winding method, and the sheet winding method. These winding methods are advantageous when applied to a fiber reinforcement impregnated with a thermosetting matrix resin having a relatively low viscosity and having draping properties (flexibility) and tackiness at room temperature. These techniques are in practical use for pipe production.
A pipe-shaped object made of a fiber-reinforced thermoplastic resin has been proposed. It is expected that this material can be molded in a shorter time than pipes made of a fiber-reinforced thermoset resin. Also, pipes made of a fiber-reinforced thermoplastic resin have superior toughness, impact resistance, vibration-damping property and other superior material properties as compared to pipes made of a fiber-reinforced thermoset resin. Additinally, fiber-reinforced thermoplastic resin pipe is receiving attention because of its suitability for recycling, which property is desirable for protection of the environment.
In the present invention, materials used for production of a fiber reinforced thermoplastic resin product containing a fiber reinforcement and a thermoplastic resin as a matrix resin is called "a fiber reinforcement-thermoplastic resin composite" or simply by "a composite". The composites are roughly divided into post-impregnation type and pre-impregnation type composites. The post-impregnation type material, which comprises a fiber reinforcement and a fibrous matrix resin (in the form of, for example, a fabric, a mat, a knit cloth) or a powdery matrix resin (where a resin powder is dispersed among filaments), has draping property (flexibility) at room temperature. This is because the reinforcement fibers have not been bonded to one another with the matrix resin. However, the material is not tacky at room temperature (generally from 20.degree. to 25.degree. C.). This type of material is described, for example, in JP-A-60-28543, JP-A-1-92232, and JP-A-2-14039. (The term "JP-A" as used herein means as "unexamined published Japanese patent application".) The pre-impregnation type material, i.e., a fiber-reinforced thermoplastic resin-impregnated material (prepreg), which is produced by impregnating a fiber reinforcement with a matrix resin, for example, by a solvent method or a hot-melt method, has neither draping property nor tackiness at room temperature. This is because the reinforcement fibers have been bonded to one another with the matrix resin. This type of material is described, for example, in JP-A-52-3985 (U.S. Pat. No. 3,742,106), JP-B-58-29651, and JP-B-4-12894 (U.S. Pat. No. 4,897,286). (The term "JP-B" as used herein means an "examined Japanese patent publication".)
Since the composites are not tacky at room temperature, and among them the prepregs also do not exhibit draping property, application of the aforementioned winding methods to composites conventionally has been difficult. It is, however, desirable to use a sheet winding method in order to take advantage of characteristics of the composites and to improve the efficiency of pipe production.
For example, the technique disclosed in International Publication No. WO 90-09272 is an application of the above winding method to the production of a cylindrical intermediate for use in molding a fiber reinforced thermoplastic resin pipe. However, the winding procedure in this technique employs a manual operation, namely, hand lay-up molding at appropriate stages. In this operation, the prepreg is provisionally fixed to the mandrel, or the prepreg is previously wound on a mandrel with a soldering iron or the like in order to prevent the wound sheet from becoming loose and to diminish interlaminar gaps. This prior art technique necessitates such a manual operation, and this results in reduced production efficiency.
The process disclosed, e.g., in JP-A-5-69492 seeks to improve such low production efficiency. In this prior art technique, a melted resin of the same kind as the matrix resin of a thermoplastic resin prepreg sheet is used as an adhesive in order to improve the efficiency of the prepreg-winding operation. However, this method still includes a manual operation.